Bellows seal for pivot joints, especially in automobiles

ABSTRACT

The invention relates to a bellows seal for pivot joints, wherein a first end of the bellows is tightly and rigidly connected to the joint housing. The second end of the bellow tightly and annularly surrounds a tappet and has a radial and sealing surface. Said surface is a front face divided into an inner concave ring surface and an outer concave ring surface. In relation to the axis of the bellow, the angle of inclination of the ring surfaces is approximately α=70° for the external ring surface and approximately β=80° for the inner ring surface. The radial extension of the outer ring surface is approximately 12% in relation to the radius of the outer ring surface of the ring flange of the second end of the bellow.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to a pivot joint with a bellows seal, inparticular for use on automobiles. At a second bellows end of thisbellows seal, the sealing of the bellows interior relative to theatmosphere is reinforced, in addition to radial sealing of the annularflange of the bellows relative to the pivot, by means of nonpositive andpositive axial bearing contact against a part which is fixedly connectedto the pivot outside the bellows.

In a pivot joint of this type, known per se from practice and fromGerman Patent document DE 44 13 664 A1, the invention is concerned withthe problem of improving the sealing effect at the second bellows end ofthe bellows seal.

The problem according to the invention is solved by a pivot joint forautomobiles having a bellows surrounding the joint to form a bellowsseal. The pivot joint includes a pivot housing, a first end of thebellows connected fixedly and leaktightly to the pivot housing, a pivot,and a second end of the bellows annularly surrounding the pivotleaktightly, wherein relative movements are possible between the secondbellows end and the pivot. In the second bellows end, having a sealingeffect, a radially outer annular contraction forms an annular flangeterminating freely on an end face. A ring assists a radial sealing ofthe second bellows end and lies in the contraction. The second bellowsend bears radially against the pivot via an approximately cylindricalsealing face which is provided with annular axially alternatingelevations and depressions having a labyrinth-like effect. Theelevations of the approximately cylindrical sealing face of the secondbellows end in each case terminate axially in a last elevation which isdesigned as an annular collar with a cylindrical inner face. Defined bythe features which are present in the bellows seal in an uninstalledstate: (1) the end face of the annular flange is divided into an innerand an outer concave annular face, of which the outer annular face isdesigned with greater concavity than the inner annular face; (2) theangles of inclination of the annular faces relative to a bellows axisare approximately α=70° for the outer annular face and approximatelyβ=80° for the inner annular face; (3) the radial extent of the outerannular face is approximately 12% in relation to the radius of the outerannular face of the annular flange of the second bellows end; (4) anannular depression is located between the annular collar, adjacent tothe inner annular face, on the inner sealing surface of the secondbellows end and this inner annular face; (5) flanks of the annularflange of the second bellows end run approximately parallel to oneanother; (6) the height of the annular flange in the region of the outerannular face measures uniformly approximately 8% of the outer diameterof the annular flange; (7) the ring is designed to be closed and made ofinelastic material and projects radially outward into an annular regionwhich is formed by the outer sealing face and in which said ring bearsaxially against the annular flange; and (8) the axial height of thecontraction is smaller than the amount by which the ring would bearpositively in this contraction, without the latter being widened, sothat, with the ring inserted, this contraction is widened as a result ofthe elastic deformation of the material of the bellows forming thiscontraction.

By virtue of the measures according to the invention, both radialsealing and axial sealing at the second bellows end are improvedconsiderably. Expedient refinements of the invention are describedherein.

The leaktightness attainable according to the invention is not achievedin bellows seals of a similar generic type, such as, for example,according to German Patent document DE-U 18 75 318 and U.S. Pat. No.3,378,286 or in the bellows seal according to German Patent document DE44 13 664 A1. This is attributable to the fact that, in these knownseals, the configuration and design of the sealing regions performingthe actual sealing function are not optimally coordinated with oneanother.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is illustrated in the drawing,in which:

FIG. 1 shows a view of a pivot joint with a screwed-on counterpiece,with a part region of the bellows being depicted in cutaway form; and

FIG. 2 shows a detail according to II in FIG. 1 of the sealing region atthe second bellows end.

DETAILED DESCRIPTION OF THE DRAWINGS

A pivot 2 is mounted tiltably and rotatably in a housing 1 of a pivotjoint via a ball head (which cannot be seen).

A bellows 3 made of elastic material effects sealing between the housing1 and the movable pivot 2. This bellows 3 is fixedly and leaktightlyconnected at its first end to the housing 1. At its second end, thebellows 3 surrounds the pivot 2 in a radially leaktight manner. Sealingis, in this case, such that rotational and sliding movements between thepivot and the bellows 3 are possible.

An annular flange 4 terminating freely on its end face is integrallyformed on the second end of the bellows 3. The end bears against thepivot. The integral forming of the annular flange 4 is such that thereis an annular contraction 5 in the transitional region to the remainingbellows body. This annular contraction 5 receives a closed inelasticring 6, by which the bellows material is tensioned against the pivot 2in a radially leaktight manner in the region of the annular flange 4.The illustration according to FIG. 2 of the detail of the sealingportions at the free end of the bellows 3, said end not being connectedfixedly to the housing 1, shows the design measures by which thecombination according to the invention of radial and axial sealing isachieved.

The respective radial sealing portion is a cylindrical portion with acylindrical sealing face having a labyrinth-like effect. Integrallyformed in this cylindrical sealing face are grooves which form annularelevations 7 and depressions 8 directly lined up axially with oneanother. In each axial end region of the cylindrical face, the lastelevation is provided as a kind of annular collar 9 with a cylindricalsealing face. The elevations located between the two outer annularcollars 9 have linear sealing edges in each case radially on the inside.

As regards the wall face which is formed by the radial inner faces ofthe annular collars 9 and the remaining elevations 7, it should also benoted, for the sake of completeness, that this is of slightly conicaldesign, with an inside diameter increasing toward the bellows interior.There is a corresponding conically receiving face on the pivot 2, ontowhich the free end of the bellows 3 is drawn leaktightly.

The end face of the annular flange 4 at the free end of the bellows 3 isformed from an inner and an outer annular face 10 and 11 runningconically. The angle of inclination of the outer annular face 11relative to the pivot axis is α=70° and the corresponding angle of theinner annular face 10 measures β=80°.

For good sealing of the annular collar 9 adjacent to the inner annularface 10, it is important that the inner annular face 10 does not mergedirectly into the annular collar 9, but via a depression 8.

The intersection point of the conical faces of the inner and outerannular faces 10 and 11 is located on a radius which is 12% smaller thanthe outer radius of the annular flange 4. The height of the annularflange 4 in relation to its outside diameter is 8%. That flank of theannular flange 4 which faces the ring 6 runs parallel to the conicalface of the outer annular face 11.

When the pivot 2 is in the state in which it is fitted to a counterpiece12, the end face having the annular faces 10 and 11 bears, in a commonplane, flat against the counterpiece, thus resulting in axial sealing inaddition to the radial sealing of the annular flange 4. The counterpiece12 must have a planar bearing face. If the counterpiece 12 consists ofmetal, its surface must have a roughness of R_(z)≦40 in order to achievesufficient axial sealing. If the metallic counterpiece 12 is a forging,its sealing surface must have a quality which is defined by c=25/tpi 80.

The axial height of the contraction 5 is slightly smaller than thediameter of the ring 6 lying in the latter. As a result, the ring 6generates, in addition to a radial tension force, an axial tension forcewhich presses the annular flange 4, via its end face, firmly andsealingly against the counterpiece 12.

For the radially outer region of the annular flange 4 to come to bearfirmly and leaktightly in the axial direction, it is important that thering 6 engages axially in a region of the annular flange 4 which is asfar outward radially as possible. This means, in other words, that theannular flange 4 projects as little as possible radially beyond theoutside diameter of the ring 6. Furthermore, it is also important, foroptimum sealing, that the annular flange 4 possesses, in its regioncorresponding to the outer annular face 11, flanks which runapproximately parallel to one another in the radial direction.

What is claimed is:
 1. A pivot joint for automobiles having a bellows surrounding the pivot joint to form a bellows seal, comprising: a pivot housing; a first end of the bellows connected fixedly and leaktightly to the pivot housing; a pivot; a second end of the bellows annularly surrounding the pivot leaktightly, wherein relative movements are possible between the second bellows end and the pivot; wherein in the second bellows end, having a sealing effect, a radially outer annular contraction forms an annular flange terminating freely on an end face; a ring assisting a radial sealing of the second bellows end lies in the contraction; the second bellows end bears radially against the pivot via an approximately cylindrical sealing face which is provided with annular axially alternating elevations and depressions having a labyrinth-like effect; the elevations of the approximately cylindrical sealing face of the second bellows end in each case terminating axially in a last elevation which is designed as an annular collar with a cylindrical inner face; wherein the pivot joint, defined by features present in the bellows seal in an uninstalled state further has: (a) the end face of the annular flange divided into an inner and an outer concave annular face, of which the outer annular face is designed with greater concavity than the inner annular face; (b) angles of inclination of the inner and outer concave annular faces relative to a bellows axis approximately α=70° for the outer annular face and approximately β=80° for the inner annular face; (c) a radial extent of the outer annular face approximates 12% in relation to a radius of the outer annular face of the annular flange of the second bellows end; (d) an annular depression located between the annular collar, adjacent to the inner annular face, on an inner sealing surface of the second bellows end and the inner annular face; (e) flanks of the annular flange of the second bellows end running approximately parallel to one another; (f) a height of the annular flange in a region of the outer annular face measuring uniformly approximately 8% of an outer diameter of the annular flange; (g) the ring designed to be closed and made of inelastic material and projecting radially outward into an annular region formed by an outer sealing face, in which the ring bears axially against the annular flange; and (h) an axial height of a portion of the contraction is smaller than the amount by which the ring would bear positively in the portion, without the latter being widened, so that, with the ring inserted, this portion is widened as a result of the elastic deformation of a material of the bellows forming this contraction.
 2. The bellows seal as claimed in claim 1, wherein the annular flange bears against a planar sealing counterface made of metal, with a machined surface having a roughness R_(z)≦40 or a forged surface with a structure of c=25/tpi
 80. 3. The bellows seal as claimed in claim 1, wherein the bellows seal is made of polychloroprene provided with slip additives.
 4. The bellows seal as claimed in claim 2, wherein the bellows seal is made of polychloroprene provided with slip additives. 